Intended Service Life Research Articles

Life Cycle Energy of Low Rise Residential Buildings in Indian Context

Life cycle energy of the building accounts for all energy inputs to the buildings during their intended service life. Buildings need to be constructed in such a way that energy consumption in their life cycle is minimal. Life Cycle Energy (LCE) consumption data of buildings is not available in public domain which is essentially required for building designers and policy makers to formulate strategies for reduction in LCE of buildings. The paper presents LCE of twenty (20) low rise residential buildings in Indian context. LCE of the studied buildings is varying from 160 - 380 kWh/m2 year (Primary). Based on the LCE data of studied buildings, an equation is proposed to readily reckon LCE of a new building.

Case Study of Remaining Service Life Assessment of a Cooling Water Intake Concrete Structure in Indonesia

This paper deals with the assessment of remaining service life of a cooling water intake concrete structure (CWICS) subjected to corrosion due to chloride attacks. Field and laboratory tests were performed to determine the current existing condition of the structure. Both destructive and nondestructive tests were employed to obtain the parameter needed for the assessment. Based on the current condition and test results, structural analysis was carried out and the remaining safety factor of CWICS was determined. From the analysis, it was found that most concrete elements of CWICS had safety factor greater than unity and might fulfil its intended service life up to the year 2033. However, fewer elements require immediate strengthening to extend their service life.

Concrete Mix Design for Service Life of RC Structures under Carbonation Using Genetic Algorithm

Steel corrosion in reinforced concrete (RC) structure is such a critical problem to structural safety that many researches have been performed for maintaining required performance during intended service life. This paper is for a numerical technique for obtaining optimum concrete mix proportions through genetic algorithm (GA) for RC structures under carbonation which is considered as a serious deterioration in underground sites and big cities. For this study, mix proportions and CO2diffusion coefficients are analyzed through the previous studies, and then the fitness function of CO2diffusion coefficient is derived through regression analysis. The fitness function from 69 test results includes 5 variables of mix proportions such as w/c (water to cement) ratio, cement content, sand content percentage, coarse aggregate content, and R.H. (relative humidity). Through GA technique, simulated mix proportions are obtained for 12 cases of verification and they show reasonable results with average relative error of 4.6%. Assuming intended service life and design parameters, intended CO2diffusion coefficients and cement contents are determined and then related mix proportions are simulated. The proposed technique can provide initial concrete mix proportions which satisfy service life under carbonation.

Tramways, Draw Works and Flumes

The settlement of the American West was directly dependent on the extraction of resources including minerals, precious metals, timber, and the commerce that resulted. The infrastructure that developed around these extraction activities was intended to be merely functional, and therefore temporary. Readily available forest resources made timber structures relatively inexpensive and easy to build; they could be put into service quickly and were adequate to immediate needs. Many of these structures survive today at former mining and milling sites, along with remnants of the railroad lines that served them. Together they provide a compelling picture of the development of the American West and the technologies used to extract, refine, and transport the materials that initiated settlement of the region. Preservation of these sites and structures poses many interesting problems: Most of the structures were designed to meet short-term needs and have already outlasted their intended service life; Most of the structures were strictly utilitarian, and maintenance of them was discontinued when mining or logging operations ceased; Exposure of these structures to severe weather conditions is typical. The structures are at remote sites and access is extremely limited; Many of the structures are dangerous due to the extent of deterioration and proximity to open mines, adits, and industrial waste. In this presentation, the authors will use three case studies to illustrate preservation issues common to remote resource extraction sites, techniques used to access the timber structures, and some of the stabilization strategies implemented at each of the sites. The case studies include the aerial tramway of the Keane Wonder Mine in Death Valley National Park, the Cable Mountain Draw Works in Zion National Park, and the Hanging Flume in Colorado.

The Study of Premature Failure of Springs Used In Railway Coaches

The springs used in the bogie suspension of railway coaches are compression springs. They are made of an elastic wire material formed into the shape of a helix. They are commonly referred to as a coil spring or a helical spring. They are used to store energy and subsequently release it to absorb shock or to maintain a force between contact surfaces. The spring returns to its natural length or position when unloaded. Springs used in railway coaches have been failing prematurely much before their intended service life. The springs are made with quality materials. Before being put to service, the springs are tested with extensive Non Destructive Testing Methods which are approved by ISO standards to make sure that quality parts are used. However the springs still fail before their service life ends.

Structural Performance of Degraded (Corroded) Reinforced Members – An Analytical Study

Any reinforced concrete structures should serve its function over the intended service life span satisfactorily. But depending upon the exposure conditions, the premature failure may takes place in the structures and it may affect its service life span too. The premature failure of the RCC structures occurs due to corrosion of the reinforcement, spalling/cracking of the reinforced concrete, improper design, improper construction, chemical ingress, etc. The corrosion of the reinforcement is the major factor behind the premature failure. This paper describes the effect of age-related deterioration (corrosion) and spalling/cracking on the structural performance of the reinforced concrete members in probabilistic terms. The effects of degradation on the probability of failure are computed to determine serviceability at various stages of degradation in reinforced concrete members. Also the paper describes and evaluates the effects which are responsible for the degradation in reinforced concrete members.

Concrete mix design for service life of RC structures exposed to chloride attack

The purpose of this research is to propose a design technique of concrete mix proportions satisfying service life through genetic algorithm (GA) and neural network (NN). For this, thirty mix proportions and the related diffusion coefficients in high performance concrete are analyzed and fitness function for diffusion coefficient is obtained considering mix components like w/b (water to binder ratio), cement content, mineral admixture (slag, flay ash and silica fume) content, sand and coarse aggregate content. Through averaging the results of 10 times GA simulations, relative errors to the previous data decrease lower than 5.0% and the simulated mix proportions are verified with the experimental results. Assuming the durability design parameters, intended diffusion coefficient for intended service life is derived and mix proportions satisfying the service life are obtained. Among the mix proportions, the most optimized case which satisfies required concrete strength and the lowest cost is selected through GA algorithm. The proposed technique would be improved with the enhancement of comprehensive data set including wider the range of diffusion coefficients.

Experimental accuracy of two dimensional strain measurements using Digital Image Correlation

The measurement of strain has always been central to developments in structural engineering. As structures around the world reach the end of their intended service life, there is a need for more robust field monitoring techniques to determine, in conjunction with numerical models, if these structures are still fit for purpose. Current strain gage technologies are only able to offer a limited number of discrete measurements, which often is not enough data to assess complex structures. This paper presents an alternative technique for measuring strain using digital images called Digital Image Correlation (DIC) that allows for the measurement of 2-D strain fields. The accuracy that can be achieved in physical experiments where sources of error such as lighting and camera quality are present is investigated. A series of tension tests on steel plates are conducted allowing measurements from the DIC technique to be compared to measurements from conventional foil strain gages. Out-of-plane motion is identified as one of the most significant potential sources of strain measurement error when using DIC. Five solutions for significantly reducing the effects of out-of-plane motion are presented and three of these solutions are applied to the steel plate experiment. Using these solutions it is possible to achieve mean strain errors of less than 5με when comparing DIC to foil strain gage measurements, which suggests that the DIC technique has the potential to replace conventional strain gages. Areas of future research are also introduced.

Carbon dioxide evaluation in a typical bridge deck replacement project

Different structures can exhibit very different characteristics in terms of embedded carbon dioxide emissions. It is therefore important that the carbon accumulation of a particular type of structure over its intended service life is properly understood before targeted measures can be taken to reduce any adverse effects. For the same type of infrastructure, considerations may vary markedly for different types of work. Within the bridge engineering sector, fibre-reinforced polymer deck has been increasingly used in deck replacement applications. However, study on its environmental performance is limited. This paper considers a typical UK highway bridge deck replacement project and evaluates two different options, including the fibre-reinforced polymer option, in carbon terms. In order to provide more general information to bridge engineers, the bridge is assumed to carry an ‘average’ volume of traffic across the highway network where it is most likely to be present. Both the embodied carbon dioxide and carbon dioxide emissions from future maintenance activities are considered. Since traffic diversion can only be considered on a project-by-project basis, parametric study is carried out to further investigate its effects. Based on the results, good practices are identified to enable engineers to reduce their carbon dioxide footprint. Uncertainties and limitations of the results are also discussed.

탄산화에 노출된 콘크리트 구조물의 배합설계에 대한 연구 - 유전자 알고리즘 적용성 평가

콘크리트 내부의 철근부식은 구조물의 안전성에 큰 영향을 주므로, 목표 내구수명동안 구조물의 성능을 확보하려는 연구가 활발하게 진행되고 있다. 이 연구는 대도시나 지하구조물에서 중요하게 평가되는 탄산화에 대하여, 유전자 알고리즘을 적용한 콘크리트 배합기법에 대한 연구이다. 이를 위해, 배합인자에 따른 이산화탄소 확산계수를 문헌조사를 통하여 분석하였으며, 습도를 고려한 최적 함수식을 회귀분석을 통하여 도출하였다. 최적 함수식은 12개의 실험자료에 대하여, 물-시멘트비, 단위 시멘트량, 잔골재율, 단위 굵은골재량, 그리고 상대습도를 포함하도록 고려하였으며, 유전자 알고리즘을 통하여, 주어진 이산화탄소 확산계수에 대한 콘크리트 배합을 도출하였다. 3개의 배합에 대하여 검증한 결과, 10% 미만의 상대오차를 보이며 주어진 배합을 잘 추정하였다. 최종적으로 서로 다른 환경과 설계 제원을 가지는 콘크리트 구조물을 가정하여, 목표 확산계수와 단위 시멘트량을 계산하였으며, 이를 이용하여 배합을 추정하였다. 제안된 기법은 주어진 확산계수와 배합을 잘 추정하였으며, 다양한 배합인자 및 혼화재료가 고려된 실험 자료를 이용한다면 더욱 합리적인 배합 기법으로 발전할 것이다.

PERFORMANCE IMPLICATIONS OF PRODUCT LIFE CYCLE EXTENSION: THE CASE OF THE A‐10 AIRCRAFT

Firms are faced with challenging decisions when capital equipment reaches the end of its designed service life. This research examines the risks of deciding to extend the retirement date of a capital asset in terms of performance and cost and offers recommended actions to mitigate this risk. Through study of the United States Air Force's A‐10 aircraft, the authors analyze one example of decreased performance and increased costs experienced when supply chain implications are not explicitly considered when making service life extension decisions. In this case, the Air Force's efforts to save money through life extension of existing aircraft actually exceeded the seemingly enormous initial investment of acquiring new aircraft. Arguments are presented suggesting the Air Force, in particular, may reap benefits from forming supply chain relationships and creating continuity plans to manage problems such as parts shortages and cost increases when extending the use of capital assets beyond its intended service life.

Seismic and Wind Load Considerations for Temporary Structures

Temporary structures such as scaffolds, shelters, tents, and facilities used during the reconstruction or repair of buildings and bridges, etc., are usually constructed for a limited-time use. Although the design of such structures to dead and live loads usually does not impose any particular challenge, their design for potential seismic or wind load requires more careful investigation. This is due to the fact that the service life of a temporary structure is much shorter than a structure, and as such, the probability of load exposure to the temporary structure is substantially less. Designing a temporary structure for the same level of seismic load exposure probability than that required for a permanent structure will not be economically viable. Seemingly, it will make sense to use a reduced design load—a level proportional to the intended service life of the structure. Using a reduced load may be a reasonable assumption for a structure that is used once. However, if the decision is to reuse the structure and to keep it for a longer time than was originally intended, a question arises as to whether, with the extended usage, the safety of the structure will be compromised. This paper provides a review of available studies on seismic and wind loads for temporary structures. Further, the use of a modified risk level, estimated based on the performance record of the structure in its initial usage cycle, is suggested. This modified risk can then be employed in making a decision on whether to allow the structure to be used longer. A simple illustrative example and several conclusions are then presented in an effort to open discussions among the structural engineering community to further elaborate on the issue of design loads for temporary structures.

Probabilistic determination of the wall thickness of an oil pipeline of a specified reliability

Within the framework of the theory of random values, an algorithm is developed that enables one to determine the mathematical expectation of oil pipeline wall thickness from the set parameter of the strength reliability and probability of durability. The solution is obtained for the case where the physicomechanical and strength characteristics of the pipe metal, the diameter, the wall thickness, the pressure, and the temperature difference have a normal distribution. The study enabled the establishment of the optimum reliability parameters of newly designed oil pipelines ensuring their failure-free operation during the intended service life.

Evaluation of Cementitious Repair Mortars for Corrosion Resistance

Repair and rehabilitation of deteriorated concrete structures are essential not only to utilize them for their intended service life, but also to assure the safety and serviceability of the associated components. A good repair improves the function and performance of the structure, thus prevents ingress of aggressive species to the steel/concrete interface and improves its durability. It is important to evaluate the performance of repair materials available for repairing the deteriorated concrete structures. This investigation was carried out to evaluate the durability characteristics of five types of modified cement based repair mortars. The corrosion resistance of the repair materials was evaluated by conducting various tests such as water absorption, rapid chloride ion penetration test, impressed voltage, 90 days ponding test, macro cell corrosion test, weight loss measurement, etc. Details of the test and their results were discussed. It is concluded that the modified cement based repair mortars formulated with different mineral admixtures (fly ash and/or silica fume) showed improved corrosion resistance.

DEVELOPMENT OF NON-DESTRUCTIVE MONITORING SYSTEM FOR CHLORIDE PENETRATION INTO REINFORCED CONCRETE STRUCTURES

Reinforced concrete structures in marine environment are subjected to chloride penetration, which significantly degrades the structural performance due to the occurrence of corrosion in the steel reinforcement. The performance degradation of the structures would reduce the intended service life and caused higher maintenance and repair cost. Therefore, system to monitor chloride penetration into reinforced concrete before the starting corrosion of reinforcement is indispensable. An embedded probe system to detect chloride penetration into concrete was developed in Japan. This probe consists of a cementitious material body and some number of wires as sensors, which are set in the shallow ditches around the probe body. The system detect the chloride penetration by monitoring the initiation time of wire corrosion, it also has the advantages of continuous monitoring and early warning on the onset of corrosion in the reinforcement. However, the probe had not yet had high sensitivity for detecting critical chloride content in concrete. Therefore to increase its sensitivity, four types of improvements, namely partial coating of the wires, waterproofing on the probe body, filling the ditches with porous material and supplying small current on the wires were evaluated in this study. From the experimental result, it was observed that supplying small current and partial coating of the wires could improve the sensitivity of the probe significantly, while waterproofing treatment on the probe body and filling the ditches did not have significant contribution.

Damage analysis for structural integrity and durability of composite materials

ABSTRACTComposite structures for mechanical and aerospace applications are designed to retain structural integrity and remain durable for the intended service life. Since the early 1970s important advances have been made in characterizing and modelling the underlying mechanical behaviour and developing tools and methodologies for predicting fracture and fatigue of composite materials. This paper presents a review of the concepts and analyses related to this area, and illustrates these by a few examples. The topics discussed are composite material strength in tension, compression and shear, damage and its progression in monotonic and cyclic loading, fatigue life prediction and damage induced changes in visco‐elastic response.

동조질량감쇠기를 장착한 강합성형 고속철도교의 피로신뢰성 평가

This study proposes a fatigue reliability evaluation procedure for steel-composite high-speed railway bridge based on dynamic analysis and investigates the effectiveness of Tuned Mass Damper(TMD) in terms of the extension of fatigue life of the bridge. For the fatigue reliability evaluation, the limit state is determined using S-N curve and linear fatigue-damage accumulation. Dynamic analyses are peformed repeatedly to consider the uncertainties of train-velocity and damping ratio of the bridge. The distribution of random variables related to fatigue damage for the intended service life is then statistically estimated from analytical results. Finally, the fatigue reliability indices are obtained by means of the Advanced First-Order Second-Moment (AFOSM) method. Through numerical simulation of a steel-composite bridge of 40m span, the effectiveness of TMD on fatigue life of the bridge is examined and the results are presented.

Bank protection devices, their types and design features. Devices of the simplest type

Shore protection devices are produced to protect the coastline from flooding and erosion. Depending on the intended service life, bank protection devices are divided into temporary and permanent. Bank protection devices of a temporary type are intended for a short service life (2-3 years) and consist in the planning of the coastal slope and strengthening it with the simplest means. Shore protection devices of a permanent type are intended for a long service life and are made in the form of bank protection clothes. The parameters of the main elements of bank protection devices for their design are given. Design schemes are given for strengthening the shore with turf, planting shrubs and brushwood lining covered with stone.

Nominal Cover Thickness Design of RC Quantitatively Considering Environment Condition by Means of Fuzzy Inference System

This article involves designing the Nominal cover thickness by means of fuzzy inference system(FIS) for quantitatively representing the environment load coefficient to reinforced concrete in corrosive environment. In this work, several variables defining the quality of concrete and environment condition, viz. environment load coefficient(ELC), were treated as fuzzy variables. To qualify ELC the environment conditions of cycle degree of wet-dry, relative humidity, distance from coast and temperature were used as input variables. To determine the Nominal cover thickness a qualified ELC, concrete grade, and water-cement ratio were used. The membership functions of each fuzzy variable were generated from the engineering knowledge based on some references as well as some international codes of practice.The restraining conditions of this work are as follows;1. The knowledge bases for generating the rule base of fuzzy inference system are derived just from some references as well as BS 8110 and BS EN 206-1/BS 8500.2. The procedure of this study is applicable only to the corrosive environments.3. It is limited to the cover to reinforcement for normal building structures with an intended service life of at least 50 years.

Probabilistic fatigue and fracture analyses of steel bridges

According to a study conducted by the ASCE Committee on Fatigue and Fracture Reliability, 80–90% of failures in steel structures are related to fatigue and fracture. Therefore, fatigue and fracture reliability is an important concern for steel bridges. In this study, the finite strip method is coupled with either the fatigue approach proposed by Wirsching, or the linear-elastic fracture mechanics (LEFM) approach as proposed by Harris (In: Sundararajan C, Ed. Probabilistic structural mechanics handbook [chapter 7]. New York: Chapman & Hall Ltd.; 1995. p 106–45.), for fatigue reliability analysis of steel highway bridges. The flat shell strips are employed to model the concrete slab and steel girders, while a connection strip is developed by means of the penalty function method in order to take into account the eccentricity of the top flange of girder. The loading effects are modeled by the fatigue truck developed by Laman and Nowak (Journal of Stuctural Engineering ASCE 1996:726). At each sampling point with given values of slab thickness and modulus ratio, a finite strip analysis of the bridge under fatigue truck is carried out, and the stress ranges at the fatigue-prone detail are calculated. According to these stress ranges and intended service life, the fatigue failure probability can be evaluated using the fatigue approach or the LEFM approach. After the failure probability is integrated over all sampling points, the fatigue reliability of the bridge is determined. Numerical examples are presented to illustrate the proposed methodology.